Piston pumps with pump cylinder and pump piston are well known from different areas of use. For example, the applicant has for some years been selling a drainage pump with the name Dominant 35c/i, which has two double-action piston/cylinder systems working in opposite directions.
Other piston pumps are described in WO 95/33924 and in EP 0 791 366, for example.
Piston pumps are exposed to forces that adversely affect their smooth running Various types of bearings, in particular roller bearings and sliding bearings, are used to support individual parts of the pump. However, these bearings are subject to wear. For example, sliding bearings or grooved ball bearings are always loaded on the same side. This leads to knocking noises. As a consequence, the bearings have to be replaced after a certain length of time. Conventional grooved ball bearings also require a certain speed of rotation in order to build up a lubricating film. If the pivoting speed of the pump cylinder is relatively low, the lubricating action is unsatisfactory. This is especially problematic in suction pumps with adjustable or controllable air flow since the pivoting speed of the cylinder also decreases when there is a reduction in the air flow.